The Nucleus

The nucleus is the cell's control center- that is, it contains the genetic information to do and make everything that goes on within a cell. The nucleus is surrounded by a nuclear envelope, which is a double membrane that protects the nucleus by filtering what can leave and enter (like the cell membrane), and separates the nucleus from the rest of the cell. The nucleus works with everything in the cell, since it has all the DNA needed to make everything. Every single protein in any cell was created because of the nucleus' DNA.

The Nuclear Envelope

The nuclear envelope is a double membrane (meaning it has a Primary/Outer and a Secondary/Inner layer) that surrounds the nucleus itself. It is made of a phospholipid bi-layer, like the cell membrane, and contains many pores for filtering. The main job of the nuclear envelope is to allow certain molecules needed inside the nucleus to pass through to get to it, while also not allowing the DNA inside the nucleus to leak into the cytoplasm. The nuclear membrane works with three main organelles: The cytoplasm, the nucleus (and nucleolus), and the Rough Endoplasmic Reticulum (Rough ER). The Rough ER actually branches off of the nuclear envelope, and is covered in many ribosomes that make proteins (see Need Some Energy for details).

The Nucleolus

The nucleolus is the granular structure inside the nucleus. It is the site where RNA is transcribed (copying DNA) and where ribosome subunits are made. The nucleolus itself is very dense and doesn't have a membrane. Its denseness actually helps protect all of the RNA, DNA, and proteins inside the nucleus that are needed for the cell to even be alive. As the core of the nucleus, the nucleolus is like the center of command. It works with every organelle in some way, whether it is making ribosomes that will make proteins for and organelle, or if RNA inside of it is copying DNA, the nucleolus is the heart of it all.

Chromasomes and Chromatin

Chromosomes and Chromatin are the little bundles in a cell's nucleolus that are needed to make everything in a cell. Made of DNA, they contain all of the genetic information possibly needed for any organelle or organelle development. But, even though they are both made of DNA, Chromosomes and Chromatin are different in a few ways...

Chromatin is unwound DNA, like an unraveled ball of yarn or a loose thread on a shirt. It can easily coil together to make Chromosomes.

Chromosomes are the little bundles of DNA mentioned earlier. Or, rather, they are the little bundles of chromatin. Chromatin gets wrapped around and histone protein inside the nucleolus to make a Chromosome.

But, no matter how different Chromosomes and Chromatin are, they both work together to work with other organelles, especially the nucleolus. The nucleolus protects the Chromosomes and Chromatin while they make proteins for ribosome subunits. Those subunits leave the nucleus and nucleolus through pores and go to make another organelle.